In my prior U.S. Pat. No. 5,230,196, which is incorporated by reference, I disclosed various collapsible structures and parts therefor that involve the use of pairs of struts, the struts of the pairs of struts both being pivotally connected to each other, and the pairs of struts being pivotally interconnected to other strut pairs, end to end, to create elongated collapsible beams. The beams formed by such interconnected strut pairs may be curved or straight, as desired, and may have straight and curved portions, as desired. I have formed a straight beam, or portion thereof, with strut pairs having two same-length struts that are connected to each other substantially at their centerpoints so that the ends of the struts define a square or rectangle. I have formed a curved beam, or portion thereof, with strut pairs having two same-length struts that are connected to each other at points equally offset from the centerpoint of the struts, so that a polygon defined by ends of the struts has two opposed parallel sides, and two opposed non-parallel sides that form an angle relative to one another.
In such collapsible structures, at the ends of the beams formed with a plurality of strut pairs, it is desirable for the ends of the struts of the two outermost strut pairs on the beam to lie substantially along the same line. In this way, the ends of the collapsible beam lie along the ground or other surface. It is, however, undesirable to cut a strut pair in order to provide this feature, such that the collapsible beam is not formed of a whole number of strut pairs. In order to provide a beam having ends that lie substantially along the same line, I use a whole number of curved strut pairs in my collapsible beam, with the number of strut pairs being determined by the angle formed by the ends of the curved strut pairs. For example, if the curved strut pairs have ends that form an angle of 30.degree., I use six curved strut pairs in my collapsible beam, if the curved strut pairs have ends that form an angle of 90.degree., I use two curved strut pairs in my collapsible beam. I prefer to use between six and twenty curved strut pairs in a collapsible beam, but can adapt my beam to use more or fewer curved strut pairs, if desired or necessary.
Collapsible structures have a wide range of uses, such as personnel shelter and aircraft hangers, and, accordingly, are desired in a wide range of sizes. In the past, when it has been necessary to provide a different size of collapsible structure, all new tooling, such as fixtures and jigs, and parts, such as straight and curved struts, had to be provided. The amount that the pivotal connection of the struts of a particular curved strut pair for a particular collapsible structure was offset from the centerpoint of those struts was selected on a case by case basis. The ends of the strut pairs along the collapsible beam are ordinarily locked together in a spaced relation by a locking member. The length of the locking member would be determined as a function of factors including the amount of the offset pivot connection, the length of the struts, and the angle desired to be defined by ends of the curved strut pairs. My prior U.S. Pat. Nos. 5,444,946, 5,274,980, 4,761,929, 4,437,275, 4,473,986, 3,968,808, and Re. 33,7190 are representative of the different structures that can be formed with interconnected struts, and of the various parts that may be incorporated in such structures, and are incorporated by reference.
I have now recognized, however, that it is possible, in collapsible structures of different sizes, to use the same general style of straight strut pairs and curved strut pairs, with the lengths of the struts all being the same and, for each curved strut pair of each collapsible structure of all of the different sizes of collapsible structures, the amount of offset of the pivotal connection of the curved strut pairs being the same. For example, in a collapsible beam formed entirely of curved strut pairs, where all of the curved strut pairs include two struts of the same length pivotally connected to one another at the same distance from the centerpoint of the struts, the length and height of the collapsible beam may be varied by providing an additional number of curved strut pairs, and by providing locking members of different lengths. If desired or necessary, additional straight strut pairs may be provided in the beam. While it may be desired to use struts having greater diameters for enhanced structural strength in collapsible beams used on larger collapsible structures, all struts may be cut to the same length, and the position of all the pivotal connection on all curved strut pairs may be kept the same. This simplifies the design of different collapsible structures, and reduces the amount of tooling necessary to produce different collapsible structures.
In accordance with one aspect of my invention, a family of collapsible structures, each collapsible structure having a collapsible beam, is provided. For each collapsible structure of the family of collapsible structures, the collapsible beam includes a plurality of strut pairs, each of the strut pairs including a first and a second strut pivotally connected to each other. The first and second struts each have a first end and a second end and are of the same length. The first ends of the first and second struts and the second ends of the first and second struts are moved closer to each other when the collapsible beam is moved toward a collapsed condition. The first ends of the first and second struts of all of the strut pairs are releasably connected in spaced relation by locking members to the second ends of the second and first struts, respectively. One or more strut pairs of the plurality of strut pairs are curved strut pairs. The first and second struts of each curved strut pair are pivotally connected to each other at points closer to the first ends of the first and second struts than the second ends of the first and second struts. Ends of first and second struts of strut pairs at opposite ends of the beam define four substantially aligned points. For different collapsible structures of the family of collapsible structures, each different collapsible structure has a different number of curved strut pairs than any other collapsible structure of the family of collapsible structures.
According to another aspect of my invention, a method of making a family of collapsible structures is disclosed. According to the method, first and second struts of a number of the curved strut pairs are pivotally connected so that the curved strut pairs are pivotally connected at points closer to the first ends of the first and second struts than the second ends of the first and second struts, the number of curved strut pairs corresponding to the type of collapsible structure of the family of collapsible structures being made.